I've learned never to load a muzzleloader rifle or pistol directly from a powder horn.
I now have a powder horn with a brass spout and a valve (spring loaded plunger). It works just like the metal powder dispensers used for cap and ball revolvers and even takes the various size spouts for those metal dispensers. Put your finger on the end of the spout, push the spring-loaded plunger while tilting over the horn, close the plunger and pour the powder into the barrel.
Since it is mechanically the same as the metal powder dispensers, I suppose it is as safe to use for a long rifle as it would be for a cap and ball revolver. It may not be period correct, but it certainly would be convenient while target shooting. Am I missing any safety issues?
Thanks,
Ron